The preferred embodiment of the PDMS can play a critical role in how water use is monitored by a utility, and in turn billed to the end user. Since the original water meters inception, there has always been, and continues to be, inaccuracy associated with very low water flow rates.
There are two general types of water meters on the market, mechanical and solid state. These meters are accurate and have served our nations communities well for many years, but these meters have limitations, they are only accurate inside a given range of flow. While these ranges are large, and cover almost all water use, very small flow still remain undetectable to both solid state and mechanical meters.
The accuracy of these existing meters is dependent on the type of water meter. Today's modern solid state water meters are extremely accurate, and can measure water flow inside its given range with close to 100% accuracy. The best solid state meter can accurately measure down to 0.03 GPM (0.03 GPM on a ¾ in pipe, this value jumps to 0.11 GPM for a 1 inch pipe). The accuracy of the PDMS preferred embodiment does not change with an increase in pipe diameter. They have proven to be reliable under a wide range of temperatures, pressures and hold up well under harsh environments. Further, these meters have no moving parts which greatly increase their reliability. The down side to this new technology is cost; many communities are hesitant to convert to this new technology for this reason.
Mechanical water meters, when measuring low flow, are the inverse of their solid state counterpart. These meters are inexpensive, however at lower flow ranges, they are inaccurate. While a solid state meter can report with a high degree of accuracy from 0.03 GPM (on a ¾ in pipe) and greater, the best mechanical water meter on the market today, will not achieve 100% accuracy until about 0.25 GPM.
Water is revenue, you can't bill for what you can't detect. Even though the low end range of detectable flow is quite good for a solid state meter, a large amount of water can still pass by the meter undetected. A flow rate of 0.03 GPM (at or below for a solid state meter is undetectable) is equal to 1.8 gallons per hour, that's a maximum of more than 43 gallons per day or 15,700 gallons per year, per customer, which the utility cannot bill for.
The revenue lost for water utility's using mechanical meters is significantly worse. The accuracy of a mechanical water meter at lower flow rates decreases with a decrease in water flow (starting at close to 100% accuracy for the best mechanical meter at 0.25 GPM, and an undetectable rate of 0.05 GPM or less). If the average flow rate were 0.14 GPM, only about 1 of this water flow would be accounted for by a mechanical water meter. That equates to more than 100 gallons of water per day that passes through the meter undetected. Annually that is more than 35,000 gallons of water per year, per customer that the utility cannot bill for.
When this data is further broken down, specifically when we take a closer look at the undetectable range, we come up with the following; 0.05 GPM is 2,160 Gallons over 30 Days, or 25,920 Gallons per year from one meter. In a community of 10,000, this could amount to 259,200,000 gallons per year (795 Acre Feet) of unbilled revenue.
The question we must ask is how many mechanical meters have leaks at or below 0.05 GPM? We do not know, as a mechanical meter cannot measure flow rates below 0.05 GPM. What we do know is that (according to the American Water Works Association) 16% of a meters usage occurs at low flow rates (less than 1 GPM) and a mechanical meter measures only a percentage of flow below ¼ GPM. This inability to record flow results in a significant loss of revenue for the utility.
For years, the insurance industry, home owners and businesses have incurred millions of dollars in losses due to unnecessary water damage. Typically the damage done is created by a small leak (such as a pinhole leak inside of a wall or slab) or a catastrophic failure in a pressurized pipe network (a burst pipe or washing machine hose failure). Presently, the most efficient way to guard against this type of leak is by continuously monitoring water flow into the structure. A tell tail sign of any water leak is continuous water flow, be it large (such as a burst water hose or pipe) or small (a pinhole leak in a copper pipe, in the slab or wall of the structure).
The purpose of the alternate embodiment of the PDMS is twofold. First, to warn of a leak condition (be it large or small) and turn off the flow of water to preventing damage to the property. And second, to indicate the amount of water being consumed by the property resulting in a more efficient use of water. Each of these tasks can be accomplished by actively monitoring the entire structure at all times.
The alternate embodiment of the PDMS is a system that monitors pressurized water flow into a home or building at all times, and when a leak is detected, will automatically shutoff water flow into the structure, and notify the party responsible.
At the present time, there are two major manufactures of continuously monitoring, whole structure leak detection systems. Both work well, but have large drawbacks, namely cost and the inability to detect very low rates of water flow, (neither unit can accurately measure, nor detect small flow rates, thus the existing units have no way of accurately measuring the amount of water leaked into the structure).
The PDMS alternate embodiment will provide the responsible party with four critical pieces of information:                A precise measurement of the amount of water which has leaked into the structure.        The amount of time which the leak has been active.        The amount of water which is flowing into the structure at any time.        The amount of water the occupant of the structure has used in accordance with their monthly water bill, and the percent remaining before a predetermined water target is met. This may be a maximum amount of water set by the water utility, or another water conserving target.        
In this respect, before explaining at least one embodiment of the Positive Displacement Metering Systems in detail it is to be understood that the design is not limited in its application to the details of construction and to the arrangement, of the components set forth in the following description or illustrated in the drawings. The Positive Displacement Metering Systems consisting of the preferred embodiment using a unique Water Fill Cylinder (WFC) with two or more sensors and the alternate embodiment using three sensors is capable of other embodiments and of being practiced and carried out in various ways. In addition, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present design. It is important, therefore, that the claims be regarded as including such equivalent construction insofar as they do not depart from the spirit and scope of the present application.